Using tribe cariceae (cyperaceae) as a model system to test ecological and evolutionary theory

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Biodiversity and its loss due to human activities is an increasing concern to biologists and understanding the origin, maintenance, and distribution of biodiversity can help conservation planning in the face of global changes in climate and levels of human activity. One difficulty in achieving this understanding is that the relative roles of natural laws, historical contingency, and chance events are hard to disentangle. Recent studies vary in approach and in scope from the phylogeny of particular families and genera, to the genetic structure of populations, to the geography of diversity hotspots. My students and I study these issues in the context of a single large lineage of plants, tribe Cariceae (Cyperaceae), commonly known as sedges. This group includes the broadly distributed genus Carex with nearly 2000 species (among 10 largest genera, globally) and four smaller genera with more restricted distributions that are nested within it. The group has a cosmopolitan distribution with most species found in temperate, boreal, arctic, alpine, and subtropical regions in a variety of habitats that vary along gradients of insolation, moisture, elevation, and nutrition. Working within a single large, diverse and widespread clade provides an unparalleled system for testing hypotheses in several fields of ecology and evolution: 1) patterns of diversification and trait evolution in relation to habitat and geographic range; 2) the relative importance of local adaptation and stochastic factors like dispersal to plant community assembly; 3) adaptive radiation and character evolution in response to different environmental conditions; and 4) patterns of species richness and endemism to guide conservation priorities. We will continue using DNA sequences to reconstruct the evolutionary history (phylogeny) of this group and use this phylogeny to study the evolutionary constraints on plant community assembly, especially in extreme environments. We will also compare the evolution of functional traits in parallel lineages of Carex that have evolved in Eastern N. America and Eastern Asia to understand constraints on the order of evolution and correlations among these traits during the past 15 million years of independent evolution.